This invention relates to a process of preparing artificial bed blocks for "Shiitake" mushroom by using lumps of spawn cultured in a container.
Generally, "Shiitake" mushroom is cultivated by using bed logs, covering the bed logs with sheets to prevent bed logs from drying, promoting growth of the mycelia under the conditions conducive to growing the mycelia and to prepare bed logs, then laying out the bed logs at an appropriate place to permit continued growth of the mycelia and the growth of "Shiitake" fruit bodies.
According to the conventional of method mentioned above, bed logs are used. However, a decrease in number of the broad-leaf trees has reduced the availability of bed logs. Thus, it makes the conventional bed log cultivation method less desirable.
Moreover, the longer cultivation period is required and a shorter period for cultivation is desired.
Another problem is the troublesome work required for such an agricultural producing method.
Intending to solve these problems, attempts to prepare artificial bed culture consisting of sawdust, rice bran or the like and have been made to cultivate "Shiitake" mushroom on such bed culture medium.
Unlike Pleurotus ostreatus, Pholiota nameko, Flammulina velutipes and other kinds of mushrooms successfully cultivated by an artificial method using bed culture medium with sawdust, rice bran, "Shiitake" is difficult to cultivate on an artificial bed culture medium and no technique for industrial level has been established so far.
One cultivation method using an artificial bed block comprises filling a bottle with sawdust, rice bran etc., inoculating, plugging the bottle to incubate in pure culture and for growing white and soft lumps of mycelium, take out the grown-up lumps of mycelium from the bottle to be sealed in a polyethylene bag and left for about a week, lumps of mycelium become an artificial bed blocks, the surface layer of the lumps of spawns turning into a brown colored hard bark layer, then removing the bed blocks from the bag to apply cooling stimulation such as immersion into cool water for appearance of mushrooms.
This method reduces contamination by various weed fungi. However, it has the disadvantage of resulting in an unstable appearance of fruit bodies of mushrooms as well as a smaller quantity. They are of poor quality, e.g. having a bad shape.
Another method is the one disclosed in the Japanese Patent Publication No. 56-99726, where a container is filled with culture medium primarily made of sawdust, the culture medium is inoculated, the culture medium shaped into a lump is taken out of the container to cut the inoculated side, a number of culture media are joined by sections, which are left for about 10 days at a temperature from 15.degree. to 20.degree. C. while sprinkling with water to grow the mycelium, said culture media are unified by the said grown mycelium, then sprinkling with water is kept for about from two and a half months to three months to prepare matured artificial bed blocks for "Shiitake" cultivation.
This method provides large sized artificial bed blocks which are easy to handle but this method also has the disadvantages associated with inferior artificial bed blocks namely the artificial bed blocks break partly and putrefy. It is not efficient to prepare bed blocks by this method.
A third method is Iizuka et al disclosed in the U.S. Pat. No. 4,071,973. In this method, the steps of growing hyphae and producing lumps of spawn are not characteristic, but the rate of appearing fruit bodies of Lentinus edodes is raised by subjecting grown-up lumps of spawn to a high and low temperature treatments alternately, and during the treatments by illuminating the surface of the lumps of spawn at definite luminous intensity. However, this method of Iizuka et al has the drawback in that the lumps of spawn are not sprinkled with water and the lumps of spawn are made susceptible to contamination by weed fungi.
A fourth method is the one which disclosed in U.S. Pat. No. 4,083,144, where a bed of culture medium is put into an air-permeable bag, inoculated with fungus seed and cultivated to give high efficiency cultivation of Lentinus edodes because of appropriate ambient air. However, this method also has the disadvantage of not sprinkling the lumps of spawn with water. Thus, the lumps of spawn are more susceptible to contamination by weed fungi.
Another method is disclosed in U.S. Pat. No. 4,083,145. This is a method for vessel cultivation of Lentinus edodes in a bed of culture medium contained in an open-topped vessel which comprises forming a plurality of open-topped seed-inoculating and air-supplying holes in the side face of the bed of culture medium and extending along the inner wall of the vessel, sterilizing said bed, then inoculating fungus seed of Lentinus edodes in the holes of the sterilized bed of said culture medium, cultivating said bed to generate hyphae of Lentinus edodes in the culture medium, then taking the bed, as a unit, out of the vessel, then subjecting the bed to mushroom-growing conditions effective to form fruit bodies of Lentinus edodes which grow from the side faces of the culture medium. This method has also the same drawbacks as the other methods mentioned-above that the lumps of spawn are more susceptible to contamination by weed fungi because they are not sprinkled with water.
The problems associated with the conventional methods of preparing artificial bed blocks for "Shiitake" cultivation prompted, the inventors to develop a method for preparing artificial bed blocks for "Shiitake" cultivation of whereby there is a stable appearance of fruit bodies and high resistance to weed fungi. Furthermore, this method also has the advantages of the cultivation method using artificial bed blocks resulting in a shorter cultivation period than is permitted by conventional bed log methods and also enables industrial production.
The inventors prepared lumps of mycelium according to the following process to find out why conventional methods using an artificial bed block result in no fruit bodies growing or a small number of fruit bodies grow and those which do grow are deformed unstable.
A culture medium, consisting of sawdust, rice-bran, and wheat-bran is filled into a polypropylene bottle or bag to be steamed for sterilization, inoculated, kept for one or two months at the optimum temperature (20.degree.-26.degree. C.) for L. edodes culturing, then the grown-up lumps of mycelium are taken out after allowing the mycelia to grow up into the cultured medium. The lumps of mycelium are removed by conventional methods using an artificial bed blocks, namely, pushing them out from polypropylene bottles or by cutting open polypropylene bags.
The lumps of mycelium at this stage are very soft, however, the hyphae are damaged when taken out in this manner. The damaged lumps of mycelium are kept cultivated for comparison with non-damaged lumps of mycelium and it was found that the damaged hyphae are less resistant to weed fungi and are less susceptible to bacterial contamination. Thus the damage caused by removing the fruit bodies causes deformed fruit bodies of mushroom having low resistivity to weed fungi. Accordingly, it was studied to develop a new removal method so that the lumps of mycelium could be removed without causing damage. During the study, it was noted that healing of damaged lumps of mycelium removed according to the conventional method is more desirable for industrial production of artificial bed blocks than to develop a method to avoid causing damage. Thus, attention was directed toward the method of healing.
The first step in the healing method was to keep the removed lumps of mycelium in a closed space having a, high humidity, i.e. humidity raised saturation or close to saturation for culturing. This allows a new aerial hypha layer to form on the whole surface of the lumps of spawn.
As the next process the second step in the healing method requires sprinkling water, water over the lumps of mycelium in open air, to achieve optimum moistening of L. edodes. The danger of weed fungi contamination was reduced by the aerial hypha layer formed during the first step which increased the resistance of the mycelium lumps to weed fungi. The result of this study gave rise to the instant invention. The study showed that the first step of the healing method lead to a new formation of aerial hypha on the lumps of spawn. The new hypha layer imparted to the spawn an increased resistance to weed fungi. The second step of the healing process allows weed fungi found on the new hypha layer to be washed off of the new aerial hypha layer surface and it also increases the activity of the spawn to produce more stable appearance of fruit body of mushroom having increased resistance to weed fungi. Consequently, the present invention was reached.